Recently, astronomers discovered a "mysterious object" outside the solar system, which is suspected to be a dwarf planet. If this discovery is confirmed, this object will become the sixth officially recognized dwarf planet in the solar system.
According to a report by CNN on October 29th, astronomers at the Vera Rubin Observatory in Chile discovered this icy object, which has been temporarily named 2026 ED138.
Astronomers at the Harvard-Smithsonian Center for Astrophysics in the United States, using computer programs to analyze observational data from the Rubin Observatory, discovered 2026 ED138. After finding more observational data on 2026 ED138 in the star catalog, they collaborated to map the object's trajectory over the past decade.
This celestial body is located about 46 astronomical units from the Sun, which is 46 times the average distance between the Earth and the Sun. Its orbit is further than that of Pluto, making it an extplanetic object.
The suspected dwarf planet outer Neptunian body 2026 ED138 at Rubin Observatory
Researchers estimate that the diameter of 2026 ED138 ranges from 600 kilometers to 1500 kilometers. It is larger than the smallest known dwarf planet, Ceres, in our solar system. Therefore, this celestial body may be large enough to form a nearly spherical shape due to its own gravity. This is a key difference between dwarf planets and asteroids, as well as other small space rocks.
Holman said that astronomers had not previously discovered this celestial body. Part of the reason is that it is located in the southern hemisphere, making it difficult to observe from the northern hemisphere. Another reason is that it lies on the same plane as the Milky Way, making it hard to distinguish from millions of other celestial bodies.
However, 2026 ED138 is currently only a candidate for a dwarf planet and cannot be identified as one yet. Holman pointed out that it may take several months to determine the actual size of this celestial body. Only if further observations confirm its status can it become the sixth officially recognized dwarf planet in the solar system.
2026 ED138 and the orbits of the other five dwarf planets: Rubin Observatory
In 2006, the International Astronomical Union defined dwarf planets as celestial bodies that orbit around the Sun, have sufficient gravity to overcome their rotational inertia, resulting in a spherical shape, and yet cannot clear other objects from their orbits. To date, the International Astronomical Union has recognized five dwarf planets: Pluto, Ceres, Makemake, Haumea, and Eris.
If 2026 ED138 is ultimately confirmed to be a dwarf planet, astronomers will first assign it a permanent number, and then determine a formal name.
Analysts point out that the discovery of a dwarf planet candidate in Neptune’s outer region is of great significance, which also demonstrates the potential of the newly built Rubin Observatory.
The Rubin Observatory is funded jointly by the National Science Foundation of the United States and the Office of Science of the U.S. Department of Energy. It is located on Mount Illpein in Pucón, Chile, and is equipped with the world's largest digital camera. Starting from early 2026, the observatory will meticulously record the entire night sky every three days. This task will last for ten years.
